On Thu, Jan 16, 2020 at 11:40:28AM -0500, Sasha Levin wrote:
From: Ondrej Jirman megous@megous.com
[ Upstream commit 50cc7e3e4f26e3bf5ed74a8d061195c4d2161b8b ]
Since 5.4-rc1, pwm_apply_state calls ->get_state after ->apply if available, and this revealed an issue with integer precision when calculating duty_cycle and period for the currently set state in ->get_state callback.
This issue manifested in broken backlight on several Allwinner based devices.
Previously this worked, because ->apply updated the passed state directly.
Fixes: deb9c462f4e53 ("pwm: sun4i: Don't update the state for the caller of pwm_apply_state") Signed-off-by: Ondrej Jirman megous@megous.com Acked-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Thierry Reding thierry.reding@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org
Note that while the patch is still correct, the problem isn't that bad any more since commit 01ccf903edd65f6421612321648fa5a7f4b7cb10 was reverted.
So .get_state is only called once during boot where the breakage doesn't hurt that much.
I let you decide if you still want to apply this patch.
Best regards Uwe